ZFS: how to replace a dead disk?

[James R. Van Artsdalen]

What's the right way to replace a dead disk under ZFS?

When ada1 failed I tried "zpool replace jwrc ada1" and when it finished
I got this:

root at cyclone ~]# zpool status
  pool: jwrc
 state: DEGRADED
status: One or more devices has experienced an error resulting in data
    corruption.  Applications may be affected.
action: Restore the file in question if possible.  Otherwise restore the
    entire pool from backup.
   see: http://www.sun.com/msg/ZFS-8000-8A
 scrub: resilver completed after 14h55m with 11 errors on Fri May 28
04:28:56 2010
config:

    NAME            STATE     READ WRITE CKSUM
    jwrc            DEGRADED     0     0    11
      raidz1        DEGRADED     0     0    23
        ada2        ONLINE       0     0     0  889M resilvered
        replacing   DEGRADED     0     0     0
          ada1/old  UNAVAIL      0  256K     0  cannot open
          ada1      ONLINE       0     0     0  1.47T resilvered
        ada3        ONLINE       0     0     0  879M resilvered
        ada4        ONLINE       0     0     0  808M resilvered

errors: 5 data errors, use '-v' for a list

---

It says "replacing" and that the device, vdev and pool are degraded, yet
the "resilver" finished hours ago.  I cannot detach the ada1/old entry.

Is there some other command I should have used to remove the dead ada1
device?

This kernel 206111, roughly April 1, on amd64